Dextromethorphan is a cough suppressant. It affects the signals in the brain that trigger cough reflex.

Doxylamine is an antihistamine that reduces the effects of natural chemical histamine in the body. Histamine can produce symptoms of sneezing, itching, watery eyes, and runny nose.

Dextromethorphan and doxylamine is used to treat cough, runny or stuffy nose, sneezing, itching, and watery eyes caused by allergies, the common cold, or the flu.

Dextromethorphan and doxylamine will not treat a cough that is caused by smoking, asthma, or emphysema.

Dextromethorphan and doxylamine may also be used for purposes not listed in this medication guide.

You should not use this medicine if you are allergic to dextromethorphan or doxylamine.

Do not use dextromethorphan and doxylamine if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, tranylcypromine, and others.

Do not give this medication to a child younger than 4 years old. Always ask a doctor before giving a cough or cold medicine to a child. Death can occur from the misuse of cough and cold medicines in very young children.

You should not use antihistamine medication to make a child sleepy.

To make sure dextromethorphan and doxylamine is safe for you, tell your doctor if you have:

• high blood pressure, heart disease;
• a thyroid disorder;
• a blockage in your digestive tract (stomach or intestines);
• liver or kidney disease;
• diabetes;
• cough with mucus, or cough caused by emphysema or chronic bronchitis;
• bladder obstruction or other urination problems; or
• if you take potassium (Cytra, Epiklor, K-Lyte, K-Phos, Kaon, Klor-Con, Polycitra, Urocit-K).

It is not known whether dextromethorphan and doxylamine will harm an unborn baby. Ask a doctor before using this medicine if you are pregnant.

Dextromethorphan and doxylamine may pass into breast milk and may harm a nursing baby. Antihistamines may also slow breast milk production. Ask a doctor before using this medicine if you are breast-feeding.

Artificially sweetened cough or cold medicine may contain phenylalanine. If you have phenylketonuria (PKU), check the medication label to see if the product contains phenylalanine.

Use Dextromethorphan And Doxylamine (Nyquil Cough) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using dextromethorphan and doxylamine and call your doctor at once if you have:

• severe dizziness or anxiety;
• a light-headed feeling, like you might pass out;
• little or no urinating; or
• liver problems--nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Common side effects may include:

• drowsiness, dizziness;
• nervousness;
• sleep problems (insomnia); or
• feeling restless or excited (especially in children).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Drinking alcohol can increase certain side effects of dextromethorphan and doxylamine.

Ask a doctor or pharmacist before using any other cold, cough, allergy, or sleep medicine. Many combination medicines contain dextromethorphan or doxylamine. Taking certain products together can cause you to get too much of this medicine.

This medicine may cause blurred vision or impair your thinking or reactions. Avoid driving or operating machinery until you know how dextromethorphan and doxylamine will affect you.